The present invention relates to scanners, and more particularly to such a scanner which is practical for scanning penetrative document as well as reflective document.
FIG. 1 shows a scanner adapted for scanning reflective document as well as penetrative document. The scanner comprises a scanning unit 80, and a light source projecting unit 90. The scanning unit 80 comprises a carriage 82 mounted on a conveying belt 83 and moved relative to document by a motor M through a gear train G and belt wheels P, a lamp holder 81 mounted on the carriage 82 and holding a lamp L1, a reflecting mirror assembly and a focusing lens respectively mounted on the carriage 82, and an image sensor for example a charge coupled device CCD for converting light from the focusing lens into a corresponding image signal. The light source projecting unit 90 comprises a conveying belt 92 mounted on belt wheels P turned by a motor M through a gear train G2, a lamp holder 91 mounted on the conveying belt 92 and holding a lamp L2. The light source projecting unit 90 is operated when the scanner is set for penetrative scanning mode for scanning penetrative document. When the scanner is set for reflective scanning mode for scanning reflective document, the light source projecting unit 90 is turned off. Because the scanning unit 80 and the light source projecting unit 90 are provided with a respective light source, much warm up time is needed when alternatively changing the scanning mode. More particularly when cathode ray tubes are used for the light sources of the scanning unit and the light source projecting unit, much warm up time is wasted. Furthermore, the installation of the two light sources greatly increase the manufacturing cost of the scanner. In order to let heat be quickly carried away from the light source of the light source projecting unit, a relatively larger housing is required.